A printed circuit board will usually contain several components and may contain one or more leadless chip carriers. Leadless chip carriers come in a variety of sizes and external pin arrangements. There are two ways to mount a leadless chip carrier to a printed circuit board. The first way is to mount a socket to the printed circuit board and then insert the leadless chip carrier into the socket making contact to the printed circuit board through the contacts located in the socket. The second way to mount a leadless chip carrier to a printed circuit board is to solder the leadless chip carrier directly to the printed circuit board. The second method is called surface mounting.
It is often desirable to monitor signals being transmitted between a leadless chip carrier and the circuit of a printed circuit board to which the leadless chip carrier is connected. In this manner, the circuit board can be tested. Monitoring signals between a leadless chip carrier and a printed circuit board provides an excellent way of troubleshooting a circuit board assembly. It is highly desirable to be able to troubleshoot a printed circuit assembly without removing the leadless chip carrier or any other components therefrom.
A device for testing socket mounting leadless chip carriers is disclosed in U.S. Pat. No. 4,516,072 issued on May 7, 1985. This device is used in testing and analyzing a printed circuit board. A test probe clips into a leadless chip carrier socket which is mounted to the printed circuit board. This test probe can then be used to test only the external circuitry on the printed circuit board. This is a very limited application for testing and troubleshooting. Moreover, this test probe cannot be used to test surface mounted leadless chip carriers.
Another example of a test probe for testing socket mounted leadless chip carriers is disclosed in U.S. Pat. No. 4,564,251 issued on Jan. 14, 1986. This leadless chip carrier adaptor also clips into a leadless chip carrier socket which is mounted to a printed circuit board. The leadless chip carrier may then be inserted into the test probe and the external circuitry, the leadless chip carrier, or both the external circuitry and the leadless chip carrier may be tested. However, this test probe is limited to testing of socket mounted leadless chip carriers and cannot be used to test surface mounted leadless chip carriers.
A device for testing surface mounted leadless chip carriers is a surface mount test clip manufactured by Minnesota Mining and Manufacturing. This surface mount test clip includes straight pins in a tall package. This test clip is limited to testing components which are spaced no closer than 0.200 inches with a pin-to-pin center spacing on the component of no less than 0.100 inches. The device uses a helical compression spring and insulating contact combs to ensure integrity of contact between the pins and the leadless chip carrier when testing. The probe also includes square contact pins to permit attachment of female socket connectors or wire wrapping to the test clip. This test clip suffers from the disadvantage that its relative height when compared to the height of the leadless chip carrier is quite large. As a result, external force applied to the test clip from attaching wires or test clips to the allotted pins protruding from the top of the test clip can make the test clip fall off of the leadless chip carrier. Also, this test clip is too large for use in densely packed circuit environments.
Accordingly, there is a need in the art for a test probe for surface mounted leadless chip carriers that can be used in densely packed circuit environments. In addition, there is a need in the art for a test probe for surface mounted leadless chip carriers having a means for remotely connecting the test probe to test components to thereby avoid application of force to the test clip from test components attached thereto.